Patent GB-1093831-A (GB)
Title: Improvements in sewing machines
IPC: D05B51/00
Filed: 1965-03-04
Abstract: 1,093,831. Sewing machines. UNION SPECIAL MACHINE CO. March 4, 1965 [March 5, 1965], No. 9200/65. Heading D1G. [Also in Division F2] The needle bar of a sewing machine driven from the arm shaft via a rotary member mounted for rotation about an axis removed from but parallel to the axis of said shaft, is balanced by means carried by said shaft to provide a first centre of mass eccentric to the axis thereof, and means carried by said rotary member to provide a second centre of mass eccentric to the axis of rotation of said member, the arrangement being such that the combinal inertia forces of said mass-providing-means provide a component in the direction of movement of the needle bar, and opposed components in a direction transverse to that of the movement of the needle bar. The arm shaft 13 carries at its free end a block 15 formed with a cut-away portion 16. A pinion 17, disposed in portion 16, fixed to a shaft 18 journalled in ball bearings 19, 20 at opposite sides of portion 16. Pinion 17 meshes with a fixed internal gear ring 21. A crank 23 on shaft 18 carries a crank pin 24 connected by a pivotal link 26 to the reciprocating needle bar 28. The pitch diameter of pinion 17 is half the pitch diameter of gear ring 21, and the axis of pin 24 is aligned with the pitch circle of pinion 17. The arrangement is thereby such that when shaft 13 rotates clockwise, the axis of shaft 18 rotates clockwise around the axis of shaft 13, shaft 18 rotates counterclockwise about its own axis, and the axis of pin 24 reciprocates vertically. Block 15 carries a semi-annular counterweight 30, the inertia force of which provides a vertical component to counterbalance the needle bar 28. The horizontal component of said inertia force is counterbalanced by a semi-annular counterweight 31 carried by an extension 23a of crank 23. Projecting radially from pin 24 is an arm 32 ending in a thread take-up finger 32a disposed parallel to pin 24. The arrangement is such that finger 32a travels in an elliptical path the major axis of which inclined preferably at 38 degrees to the horizontal, and its length is about 1¢ times that of the minor axis. Pin 24 passes through a vertical slot 33a in a plate 33 secured together with a member 34 to the machine head 11. Member 34 is provided with an opening 34b corresponding to the path of movement of finger 32a. Provided within opening 34b is a plate 35 spaced from opening 34b to provide a slot for the passage of finger 32a, the latter also passing through an offset portion 36b of a bracket 36 securing plate 35 to head 11. A closure member 38 is pivoted at 39b to head 11 and is formed with an elliptical groove 38b receiving fingers 32a. Member 38 is held by a spring catch 40 in the closed position, and is then spaced from member 34 by a thread-passing gap 38c. A thread-guiding pin 41 projects inwardly from member 38 through an aperture in plate 35. Thread passes from a tensioner positioned at one side of head 11 over finger 41, and is led to the needle via guides positioned on the other side of head 11. A knife blade 37 is provided in the offset portion 36b for severing slack thread resulting from thread breakage. The presser bar 53 is provided with a radially-projecting arm 63 overlying one arm 60 of a two-armed lever pivoted at 61 on a fixed bracket 62. Arms 60 and 63 pass through a slot in a vertical bar 59 connected to a treadle. The other lever arm 60a passes through a slot in a vertical bar 65 which is slidably mounted in bracket 62, and is formed with a cam notch accommodating the tension-releasing pin 45d of the thread tensioner. When said treadle is actuated to raise bar 59 arm 60 is also raised to lift the presser bar via arm 63, and arm 60a is lowered to engage a block 64 on bar 65 for depressing the latter, whereby pin 45d is actuated to release the thread tension.